AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The carbon cycle returns carbon from organisms to the atmosphere as carbon…
Full specification wording
How materials are cycled: The carbon cycle returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis.
Carbon is stored in living organisms in compounds such as carbohydrates, proteins and lipids.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 4 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Carbon is stored in living organisms in compounds such as carbohydrates, proteins and lipids. The carbon cycle moves this carbon back to the atmosphere as carbon dioxide, which plants then take in for photosynthesis. Key return processes include respiration by plants, animals and microorganisms, which releases carbon dioxide; decomposition of dead organisms and waste by microorganisms, which also releases carbon dioxide; and combustion of fossil fuels and other organic material, which releases carbon dioxide. The carbon dioxide in the atmosphere is then available to producers, which use it to make glucose and other organic compounds. In this way carbon is continuously recycled between organisms and the atmosphere.
What earns the marks
- Respiration in plants, animals and microorganisms releases carbon dioxide into the atmosphere.
- Decomposition of dead organisms and waste by microorganisms returns carbon dioxide to the atmosphere.
- Combustion of fossil fuels and other organic matter releases carbon dioxide into the atmosphere.
- Plants absorb carbon dioxide from the atmosphere and use it in photosynthesis to produce glucose and other organic compounds.
- The carbon cycle therefore links carbon stored in organisms with atmospheric carbon dioxide, allowing carbon to be reused by producers.
Common mistakes and how to put them right
Saying that plants take in carbon dioxide only at night.
Put it right: Plants take in carbon dioxide during photosynthesis in the light, while respiration occurs continuously.
Confusing the carbon cycle with the nitrogen cycle.
Put it right: The carbon cycle returns carbon as carbon dioxide, whereas the nitrogen cycle involves nitrogen compounds such as nitrates and ammonia.
Stating that respiration only occurs in animals.
Put it right: Plants and microorganisms also respire and release carbon dioxide.
Exam tips
- Name the specific process that returns carbon to the atmosphere, such as respiration, decomposition or combustion, rather than saying 'carbon is released'.
- When describing photosynthesis, state that carbon dioxide is used to make glucose, not just that plants 'take in' carbon dioxide.
- Use a flow diagram or labelled arrows to show carbon moving from organisms to the atmosphere and back to plants, which makes the cycle clear.
Try the lesson
The start of the How materials are cycled: The carbon cycle returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis. lesson, made from checked teaching notes for this specification point.
Have a go first
Which process in the carbon cycle returns carbon dioxide to the atmosphere from living organisms?
Listen
Carbon is stored in living organisms in compounds such as carbohydrates, proteins and lipids. The carbon cycle moves this carbon back to the atmosphere as carbon dioxide, which plants then take in for photosynthesis. Key return processes include respiration by plants, animals and microorganisms, which releases carbon dioxide; decomposition of dead organisms and waste by microorganisms, which also releases carbon dioxide; and combustion of fossil fuels and other organic material, which releases carbon dioxide. The carbon dioxide in the atmosphere is then available to producers, which use it to make glucose and other organic compounds. In this way carbon is continuously recycled between organisms and the atmosphere. A strong answer earns marks for these points. Respiration in plants, animals and microorganisms releases carbon dioxide into the atmosphere. Decomposition of dead organisms and waste by microorganisms returns carbon dioxide to the atmosphere. Combustion of fossil fuels and other organic matter releases carbon dioxide into the atmosphere. Plants absorb carbon dioxide from the atmosphere and use it in photosynthesis to produce glucose and other organic compounds. A common slip: Saying that plants take in carbon dioxide only at night. Instead, plants take in carbon dioxide during photosynthesis in the light, while respiration occurs continuously. Exam tip: Name the specific process that returns carbon to the atmosphere, such as respiration, decomposition or combustion, rather than saying 'carbon is released'.
See it
Key words
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Carbon cycle
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Respiration
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Decomposition
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Combustion
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See every definition
- Carbon cycle
- Returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis, so carbon is continuously recycled between organisms and the atmosphere.
- Respiration
- A return process by plants, animals and microorganisms which releases carbon dioxide into the atmosphere.
- Decomposition
- A return process in which microorganisms break down dead organisms and waste, releasing carbon dioxide into the atmosphere.
- Combustion
- A return process in which fossil fuels and other organic material are burned, releasing carbon dioxide into the atmosphere.
Label the diagram
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1Box 1
2Box 2
3Box 3
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